1. Department of Radiology, The Third People's Hospital of Hainan, Sanya, Hainan 571100, P.R. China
2. Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
3. Department of Ultrasound, Sanya Maternity and�Child�Health Care�Hospital, Sanya, Hainan 572000, P.R. China